﻿/************************************************************************

   Extended Silverlight Toolkit

   Copyright (C) 2010-2012 Xceed Software Inc.

   This program is provided to you under the terms of the Microsoft Public
   License (Ms-PL) as published at http://extendedsilverlight.codeplex.com/license

   Please purchase a commercial version of this toolkit if you are using
   it in a commercial product. The commercial versions support the project,
   and also include more features for each control, priority support,
   source code, updates, removed watermark, and a proprietary license.

   Visit http://xceed.com and follow @datagrid on Twitter.

  **********************************************************************/

using System.Diagnostics;

namespace Xceed.Silverlight.Data
{
  internal abstract class SourcePosition
  {
    #region Static Fields

    internal static readonly SourcePosition BeforeFirst = new BeforeFirstPosition();
    internal static readonly SourcePosition AfterLast = new AfterLastPosition();

    #endregion Static Fields


    internal SourcePosition()
    {
    }


    #region IsOutOfBound Property

    public bool IsOutOfBound
    {
      get
      {
        return ( this.IsBeforeFirst || this.IsAfterLast );
      }
    }

    #endregion IsOutOfBound Property

    #region IsBeforeFirst Property

    public virtual bool IsBeforeFirst
    {
      get
      {
        return false;
      }
    }

    #endregion IsBeforeFirst Property

    #region IsAfterLast Property

    public virtual bool IsAfterLast
    {
      get
      {
        return false;
      }
    }

    #endregion IsAfterLast Property


    #region Private BeforeFirstPosition Nested Type

    private class BeforeFirstPosition : SourcePosition
    {
      public override bool IsBeforeFirst
      {
        get
        {
          return true;
        }
      }

#if DEBUG
      public override string ToString()
      {
        return "Before First";
      }
#endif  //DEBUG
    }

    #endregion Private BeforeFirstPosition Nested Type

    #region Private AfterLastPosition Nested Type

    private class AfterLastPosition : SourcePosition
    {
      public override bool IsAfterLast
      {
        get
        {
          return true;
        }
      }

#if DEBUG
      public override string ToString()
      {
        return "After Last";
      }
#endif  //DEBUG
    }

    #endregion Private AfterLastPosition Nested Type
  }
}
